1. Field of the Invention
The present invention relates to the detection and identification of micron-sized particles including liquids, biological microorganisms, chemical particles and unknown analytes. It also pertains to the construction of special particles for test or manufacturing purposes.
2. Description of the Prior Art
The recognition of agents of biological origin and the identification of unknown microorganisms in a sample of micron-sized particles has received much attention in the recent past. The threat caused by biological weapons was widely publicized during recent military operations in the Middle East. As a result of that military experience, it was recognized that detection of a biological threat is significantly different from the detection of a chemical threat.
One of the major differences is that biological particles in an aerosol may be significant at concentrations which are thousands to tens of thousands of times less than chemical threat concentrations. A single microorganism in a background of 100-1,000 particles of battlefield dust may be only double the background level but nonetheless be a lethal threat.
It is possible to measure changes which are quite small compared to a typical background of battlefield dust, with instruments which recognize single particles as they are processed one by one at a total rate of thousands per second. It is also feasible to make such determinations under field conditions by adding micron-sized amounts of reagent (such as antibodies) to particular threats on a particle by particle basis and to detect the presence or absence of the threat in each particle with a fluorescent marker. Research to develop a UV fluorescence point sensor to detect individual particles with biological type fluorescent signatures is promising. Microorganisms will trigger the device but the auto-fluorescent signature is not unique. There are indications, however, that each microorganism may have a unique fluorescent signature and additional research is being conducted in this area.
Electrodynamic balances are known to exist which have been used to suspend micron-sized particles in an alternating electric field for indefinitely long periods of time by adding solid or liquid materials to the suspended particles in amounts which are less than or equal in volume to the original particle.
This serves the following purposes:
1. to test the microparticle for physical or chemical changes as compared to the particle without the added material; PA1 2. to use the additive as a test for the presence of a given chemical or biological component of the unknown particle; PA1 3. to do sequential tests of the type mentioned in paragraph 2, above, on the same particle; PA1 4. to add known components in an effort to form particles of a desired type with highly specified properties. PA1 1. adding material to the particle in the gas phase; PA1 2. squirting a second charged particle in the chamber in an uncontrolled way in hopes that it will collide with the first particle and stick to it; PA1 3. adding the additional material to the bulk material before suspending the particle; PA1 4. adding a droplet to the first particle attached to a microscope slide.
The prior art has injected the additive in the following ways: